(A first aspect of the invention) This invention relates to a charging apparatus for a capacitor storage type power source for electrically charging a capacitor storage type power source storing electric energy in electric double layer capacitors.
The terminal voltages can fluctuate to a large extent in a high voltage and large capacity energy storage type power source, which is formed by connecting a plurality of electric double layer capacitors in series, as a function of the quantity of charged or discharged electric energy. Such a capacitor storage type power source operates inefficiently and gives rise to a problem of withstand current because a large charge current flows in the initial stages of a charging process when charged with electric energy at a constant voltage like a secondary battery. Therefore, such a capacitor storage type power source is charged with electric energy efficiently by way of a constant current charge process. In an energy storage type power source including electric double layer capacitors, a reference value is defined for the charge voltage of the electric double layer capacitors and a parallel monitor is connected to each electric double layer capacitor to limit the terminal voltage of the capacitor, bypassing the charge current, when the terminal voltage (charge voltage) exceeds the reference value because the capacitors that are connected in series can show variances of charge voltage.
Each of the parallel monitors bypasses the charge current in this way to limit the charge voltage to a predetermined level (full charge voltage that is lower than the withstand voltage) to reduce the variances of charge voltage among the electric double layer capacitors. However, as the charge voltages of the electric double layer capacitors rise and the parallel monitors sequentially operate to bypass the charge current, the power loss increases in proportion to the operation time and the number of parallel monitors operating to bypass the charge current. Therefore, it is necessary to avoid a situation where the parallel monitors operate to bypass a large charge current for a long time. Additionally, the charging apparatus for electrically charging an energy storage type power source is required to have a power limiter feature of switching from constant current charge to constant power charge when the charge voltage of the entire energy storage type power source rises above a predetermined level due to constant current charge typically by reducing the charge current in response to the rise of the charge voltage (See, for example, Michio Okamura, “Electric Double-Layer Capacitor and Electricity Accumulation System”, The Nikkan Kogyo, Shimbun, Ltd., 3rded. Sep. 30, 2005, pp. 138-139 and Japanese Patent Publication No. 3306325).
(A second aspect of the invention) The present invention relates to a charging apparatus for a capacitor storage type power source for electrically charging a capacitor storage type power source storing electric energy in electric double layer capacitors by controlling the charge current, modulating the pulse width by means of a pulse width modulation means from a charge power source.
The terminal voltages can fluctuate to a large extent in a high voltage and large capacity energy storage type power source, which is formed by connecting a plurality of electric double layer capacitors in series, as a function of the quantity of charged or discharged electric energy. Such a capacitor storage type power source operates inefficiently and gives rise to a problem of withstand current because a large charge current flows in the initial stages of a charging process when charged with electric energy at a constant voltage like a secondary battery. Therefore, such a capacitor storage type power source is charged with electric energy efficiently by way of a constant current charge process. In an energy storage type power source including electric double layer capacitors, a parallel monitor is connected to each electric double layer capacitor to limit the terminal voltage (charge voltage) of the capacitor, bypassing the charge current at a predetermined reference voltage because the capacitors that are connected in series can show variances of charge voltage. Each of the parallel monitors bypasses the charge current in this way to limit the charge voltage to a predetermined level (full charge voltage that is lower than the withstand voltage) to reduce the variances of charge voltage among the electric double layer capacitors. However, as the charge voltages of the electric double layer capacitors rise and the parallel monitors sequentially operate to bypass the charge current, the power loss increases and the parallel monitors have a withstand current upper limit. Therefore, it is necessary to avoid a situation where the parallel monitors operate to bypass a large charge current for a long time. Additionally, the charging apparatus for electrically charging an energy storage type power source is required to have a power limiter feature of switching from constant current charge to constant power charge when the charge voltage of the entire energy storage type power source rises above a predetermined level due to constant current charge typically by reducing the charge current in response to the rise of the charge voltage (See, for example, Michio Okamura, “Electric Double-Layer Capacitor and Electricity Accumulation System”, The Nikkan Kogyo Shimbun Ltd., 3rd ed. Sep. 30, 2005, pp. 134-139 and Japanese Patent Publications No. 2894444 and No. 3306325).
(On the third aspect of the invention) The present invention relates to a charging apparatus for electrically charging a capacitor storage type power source including a plurality of electric double layer capacitors connected in series for storing electric energy and having respective parallel monitors for bypassing the charge current at a predetermined voltage.
The terminal voltages can fluctuate to a large extent in a high voltage and large capacity energy storage type power source, which is formed by connecting a plurality of electric double layer capacitors in series, as a function of the quantity of charged or discharged electric energy. Such a capacitor storage type power source operates inefficiently and gives rise to a problem of withstand current because a large charge current flows in the initial stages of a charging process when charged with electric energy at a constant voltage like a secondary battery. Therefore, such a capacitor storage type power source is charged with electric energy efficiently by way of a constant current charge process. In an energy storage type power source including electric double layer capacitors, a parallel monitor is connected to each electric double layer capacitor to limit the terminal voltage (charge voltage) of the capacitor, bypassing the charge current at a predetermined reference voltage because the capacitors that are connected in series can show variances of charge voltage.
Each of the parallel monitors bypasses the charge current in this way to limit the charge voltage to a predetermined level (full charge voltage that is lower than the withstand voltage) to reduce the variances of charge voltage among the electric double layer capacitors. However, as the charge voltages of the electric double layer capacitors rise and the parallel monitors sequentially operate to bypass the charge current, the power loss increases. Additionally, there is an upper limit for the withstand current of the parallel monitors. Therefore, it is necessary to avoid a situation where the parallel monitors operate to bypass a large charge current for a long time (See, for example, Michio Okamura, “Electric Double-Layer Capacitor and Electricity Accumulation System”, The Nikkan Kogyo Shimbun Ltd., 1st ed. Mar. 31, 1999, pp. 135, 145-159 and Japanese Patent Publication No. 3306325).
(A fourth aspect of the invention) The present invention relates to a charge/discharging apparatus for a capacitor storage type power source adapted to charge and discharge a capacitor storage type power source for storing electric energy in electric double layer capacitors, the capacitor storage type power source having a main switching circuit to be turned on/off according to an on/off signal and a synchronous rectifier circuit to be turned on/off at phases inverse relative to the main switching circuit to store electric energy in electric double layer capacitors by accumulating energy in a choke coil at the on time of the main switching circuit and discharging the energy accumulated in the choke coil by turning on the synchronous rectifier circuit at the off time of the main switching circuit.
The terminal voltages can fluctuate to a large extent in a high voltage and large capacity energy storage type power source, which is formed by connecting a plurality of electric double layer capacitors in series, as a function of the square root of the quantity of electric energy stored in the capacitors. Thus, a PWM (pulse width modulation) control technique is employed in such a charge/discharging apparatus for an energy storage type power source so as to make it efficiently follow the terminal voltages that can fluctuate to a large extent by changing the pulse width to control the charge/discharge operation in a desired manner.
In a switching power source apparatus for storing electric energy in a choke coil by turning on/off a main switching circuit and discharging the stored electric energy by way of a rectifier diode, the ratio of the loss produced by the rectifier diode rises when obtaining a low voltage DC output. Therefore, the synchronous rectifier circuit (switching circuit) that is turned on/off at phases inverse relative to a main switching circuit is replaced by a rectifier diode to reduce the loss. A charge/discharging apparatus for a capacitor storage type power source that employs a PWM control technique can improve the charge/discharge efficiency by using a synchronous rectifier circuit (see, for example, Michio Okamura, “Electric Double-Layer Capacitor and the Electricity Accumulation System”, The Nikkan Kogyo Shimbun Ltd., 3rd ed. Sep. 30, 2005, pp. 133-142 and Japanese Patent Publication No. 3626072).
(A fifth aspect of the invention) The present invention relates to a charging apparatus for a capacitor storage type power source adapted to charge a capacitor storage type power source for storing electric energy in electric double layer capacitors by pulse width modulation by means of a pulse width modulation means from a charge power source.
The terminal voltages can fluctuate to a large extent in a high voltage and large capacity energy storage type power source, which is formed by connecting a plurality of electric double layer capacitors in series, as a function of the quantity of charged or discharged electric energy. When solar cells are employed as a charge power source for an energy storage type power source including electric double layer capacitors, they have to be controlled by taking their characteristics into consideration. This is because solar cells have a maximum power point MPP, as shown in FIG. 37B, of the accompanying drawings and other specific characteristics. The specific characteristics of a solar cell include a hill-shaped power characteristic having its peak at the maximum power point MPP and a voltage-current characteristic that the electric current decreases from a maximum current Imax to 0 as the voltage rises until the maximum voltage Vmax is reached while the electric current steeply falls when the voltage passes the maximum power point MPP. These characteristics fluctuate depending on sunlight and the ambient temperature.
To improve the charge efficiency from solar cells, it is preferable to arrange a DC/DC converter between the solar cells and the energy storage type power source so as to make them operate as maximum power point tracker (MPPT) that tracks the maximum power point (MPP) if sunlight changes and also make the converter operate as current source for the electric double layer capacitors. Then, the output power of the solar cells is subjected to A/D conversion to produce digital data and the obtained digital data are controlled by a microcomputer. More specifically, the load of the solar cells is made to fluctuate minutely and data on the fluctuations are collected. Then, the obtained data are averaged and/or otherwise processed and the processed data are compared with the preceding corresponding data to see if the MPP is directed to the rising side or the falling side of the load current. Then, the load of the solar cells is fed back for the purpose of maximizing the output power (See, for example, Michio Okamura, “Electric Double-Layer Capacitor and Electricity Accumulation System”, The Nikkan Kogyo Shimbun Ltd., 3rd ed. Mar. 31, 1999, pp. 184-188, 191-194 and Japanese Patent Publication No. 3559803).
(A sixth aspect of the invention) The present invention relates to a capacitor storage type power source adapted to generate solar power by means of solar cell panels and store the generated power in capacitors such as electric double layer capacitors.
The shift of energy source from fossil fuel to natural energy sources has been discussed in recent years in various fields. Particularly, solar power generation by means of solar cells is expected to provide power generation systems in the future because, unlike other natural energy sources, it can be realized with ease by arranging solar cells on the roofs and/or walls of buildings without entailing any nuisances such as noises.
Meanwhile, capacitors such as electric double layer capacitors are non-Faradic devices that can store electric energy only by exploiting physical phenomena and hence differ from batteries that utilizes chemical reactions. Thus, capacitors can realize a charge/discharge efficiency higher than 90%, a cycle life of a million times and a service life longer than 10 years, which are beyond conceivability for chemical batteries. Charging apparatus for capacitor storage type power sources have been proposed to generate solar power by means of solar cells and stores the generated power in capacitors such as electric double layer capacitors.
FIG. 45 illustrates the relationship of the output current, the output voltage and the output power of a solar cell. FIG. 45 shows the output characteristics of a solar cell under certain sunshine conditions and certain temperature conditions. In FIG. 45, the horizontal axis indicates the solar cell current “A” and the vertical axis indicates the solar cell voltage “V” and the solar cell output power “W”. In FIG. 45, the solid line shows the I-V characteristic of the cell, while the dotted line shows the output power characteristic (I-P characteristic). Referring to FIG. 45, as the load of the solar cell, or the solar cell voltage, is changed from 1.7V to 0.5V, the output current of the solar cell increases from 0 A to about 0.3 A but the output power of the solar cell shows a maximum value of about 0.3 W at or near 0.23 A (maximum power Pmax) and rapidly falls below 0.1 W beyond that current value. Thus, the output power of a solar cell shows a characteristic curve having a peak value. The output characteristic of a solar cell changes as a function of on the sunshine conditions and the temperature conditions and the maximum power Pmax changes accordingly. A maximum power point tracking (MPPT) control method is known for constantly taking out a maximum power Pmax in order to raise the generation efficiency and popularly being used.
Capacitors such as electric double layer capacitors are described in Michio Okamura, “Electric Double-Layer Capacitor and Electricity Accumulation System”, The Nikkan Kogyo Shimbun Ltd., 3rd ed. Sep. 30, 2005 and Japanese Patent Application Laid-Open Publication No. 2006-59126 discloses an MPPT control method for solar cells.
(A seventh aspect of the invention) The present invention relates to a charging apparatus for capacitor storage type power source that are very suitable for storing electric energy in capacitors such as electric double layer capacitors.
Capacitor chargers are provided with a constant voltage mode (CV mode), a constant current mode (CC mode) and a constant power mode (CP mode). Capacitors can be charged with electricity efficiently if it is charged in a constant current mode (CC mode) in the initial stages of the charge process, subsequently in a constant power mode (CP mode) and finally in a constant voltage mode (CV mode) when the process approaches a fully charged condition.
A technique of PWM (pulse width modulation) control that employs a switching converter is used for capacitor chargers in order to realize a stable power supply. Then, the charge process is controlled in a desired manner by changing the pulse width for the constant voltage mode (CV mode), the constant current mode (CC mode) and the constant power mode (CP mode). With a switching converter, the DC power applied to the primary winding side of the transformer of the switching converter is periodically turned on and off and the AC power induced at the secondary winding side of the transformer is rectified and smoothed so as to obtain DC power as output power with a voltage shift. A charge method and a charger are described in detail in Michio Okamura, “Electric Double-Layer Capacitor and Electricity Accumulation System”, The Nikkan Kogyo Shimbun Ltd, 3rd ed. Sep. 30, 2005, pp. 135-137 and Japanese Patent Application Laid-Open Publication No. H7-87668. FIG. 50 illustrates the waveform of the electric current that is produced at the primary side of the transformer of a switching converter. As shown in FIG. 50, the electric power of the Ton period is taken out at the secondary side out of each period T.
(A eighth aspect of the invention) The present invention relates to a charge or discharging apparatus for a capacitor storage type power source adapted to charge or discharge, whichever appropriate, a capacitor storage type power source having a main switching circuit to be turned on/off according to an on/off signal and a choke coil with electric energy.
The terminal voltages can fluctuate to a large extent in a high voltage and large capacity energy storage type power source, which is formed by connecting a plurality of electric double layer capacitors in series, as a function of the square root of the quantity of electric energy stored in the capacitors. Thus, a PWM (pulse width modulation) control technique is employed in such a charge or discharging apparatus for an energy storage type power source so as to make it efficiently follow the terminal voltages that can fluctuate to a large extent by changing the pulse width to control the charge/discharge operation (e.g., switching of constant current control CC, constant power control CP and constant voltage control CV) in a desired manner.
In a switching power source apparatus for storing electric energy in a choke coil by turning on/off a main switching circuit and discharging the stored electric energy by way of a rectifier diode, the ratio of the loss produced by the rectifier diode rises when obtaining a low voltage DC output. Therefore, the synchronous rectifier circuit (switching circuit) that is turned on/off at phases inverse relative to a main switching circuit is replaced by a rectifier diode to reduce the loss. A charge/discharging apparatus for a capacitor storage type power source that employs a PWM control technique can improve the charge or discharge efficiency by using a synchronous rectifier circuit (see, for example, Michio Okamura, “Electric Double-Layer Capacitor and Electricity Accumulation System”, The Nikkan Kogyo Shimbun Ltd., 3rd ed. Sep. 30, 2005, pp. 135-137 and Japanese Patent Application Laid-Open Publication No. H7-87668).
(A ninth aspect of the invention) The present invention relates to a discharging apparatus for discharging electric energy from a capacitor storage type power source for storing electric energy in electric double layer capacitors to a load.
The terminal voltages can fluctuate to a large extent in a high voltage and large capacity energy storage type power source, which is formed by connecting a plurality of electric double layer capacitors in series, as a function of the square root of the quantity of electric energy stored in the capacitors. Thus, a PWM (pulse width modulation) control technique is employed in such a discharging apparatus for an energy storage type power source so as to secure a stable power supply from the largely fluctuating terminal voltages for control purposes by changing the pulse width to control the charge/discharge operation (e.g., switching of constant current control CC, constant power control CP and constant voltage control CV) in a desired manner.
In a switching power source apparatus for storing electric energy in a choke coil by turning on/off a main switching circuit and discharging the stored electric energy by way of a rectifier diode, the ratio of the loss produced by the rectifier diode rises when obtaining a low voltage DC output. Therefore, the synchronous rectifier circuit (switching circuit) that is turned on/off at phases inverse relative to a main switching circuit is replaced by a rectifier diode to reduce the loss. A discharging apparatus for a capacitor storage type power source that employs a PWM control technique can improve the charge or discharge efficiency by using a synchronous rectifier circuit (see, for example, Michio Okamura, “Electric Double-Layer Capacitor and Electricity Accumulation System”, The Nikkan Kogyo Shimbun Ltd., 3rd ed. Sep. 30, 2005, pp. 135-137 and Japanese Patent Application Laid-Open Publication No. H7-87668).
(A tenth aspect of the invention) The present invention relates to a discharging apparatus for discharging electric energy from a capacitor storage type power source for storing electric energy in electric double layer capacitors to a load.
The terminal voltages can fluctuate to a large extent in a high voltage and large capacity energy storage type power source, which is formed by connecting a plurality of electric double layer capacitors in series, as a function of the square root of the quantity of electric energy stored in the capacitors. Thus, a discharging apparatus according to the invention comprises a regulated power supply circuit so as to secure a stable power supply from the largely fluctuating terminal voltages for control purposes and a PWM (pulse width modulation) control technique is employed so as to make it efficiently follow the terminal voltages that can fluctuate to a large extent by changing the pulse width to control the charge/discharge operation (e.g., switching of constant current control CC, constant power control CP and constant voltage control CV) in a desired manner.
In a switching power source apparatus for storing electric energy in a choke coil by turning on/off a main switching circuit and discharging the stored electric energy by way of a rectifier diode, the ratio of the loss produced by the rectifier diode rises when obtaining a low voltage DC output. Therefore, the synchronous rectifier circuit (switching circuit) that is turned on/off at phases inverse relative to a main switching circuit is replaced by a rectifier diode to reduce the loss. A charge/discharging apparatus for a capacitor storage type power source that employs a PWM control technique can improve the charge or discharge efficiency by using a synchronous rectifier circuit (see, for example, Michio Okamura, “Electric Double-Layer Capacitor and Electricity Accumulation System”, The Nikkan Kogyo Shimbun Ltd., 3rd ed. Sep. 30, 2005, pp. 135-137 and Japanese Patent Application Laid-Open Publication No. H7-87668).